Gentleman, I am coming in on the end of the story, but let me add the following possibility:
[NOTE: I do not offer this information as fact, but wonder if it is possible.]
From my 7th Miss. Inf. "Lest We Forget" Roster I have listed:
Sharpe, H. S. Pvt. Co. C “Not mustered” per the Wm.Hadskey Roster which in most cases meant that the man enlisted, but was impatient and joined another unit before the regiment was mustered for service. [See H.H. Sharpe Co. A 9th Miss. Surr. NC. Parole Roster May 1, 1865. The majority of this company was comprised of the remnants of the 7th Regt. Miss. Inf.; however, there were several men not previously part of the 7th Miss. on the parole roster,one being H.H. Sharpe who had been in Co. F Jeff Davis Legion, Cav.].
If this is in fact the same man, why couldn't men from the 4th Cav. 1st Miss. Light Arty. also have made such a decision and joined their comrades as they returned to the fight?
I think it is possible that men from Cav. regiments and artillery units that had either been disbanded or were not capable of sustaining the war effort in Miss. or La. may have joined their comrades at Meridian and returned to the war effort with the Army of Tennessee as it returned to the North Carolina campaign in March of 1865.
Let me repeat: I do not offer this information as fact, but wonder if it is possible.